Control system



Sept. 5, 1944. w. A. RAY 2,357,609

CONTROL SYSTEM Filed Oct. 50, 1942 3nventor:

WILLIAM A. QAY,

a flaw,

Gttorneg.

Patented Sept. 5, 1944 UNITED STATES PATENT OFFICE CONTROL SYSTEM William A. Ray, Los Angeles, Calif.

Application October 30, 1942, Serial No. 463,919

6 Claims.

My present invention relates to systems for controlling the operation of fluid-fuel consuming burners, from a point remote therefrom, by the aid of carrier-frequency current conducted over the electrical service lines.

An object of this invention is to provide, in a system of the character described, means for rendering the system ineffective to pass fuel to the burner in the event of extinguishment of the pilot burner flame, or of the flame of the main burner when the same is of the normally-uncxtinguished type adapted to be controlled between low and high fire conditions.

A more specific object is to provide, adjacent the burner, means including an electronic circuit selectively responsive to the carrier-frequency and wherein flame responsive means forms an essential element; an electrically operated fuel-controlling valve energized, directly or indirectly, by the rectified carrier-frequency current; and, at the remote control point, a combination thermostat and carrier-frequency generator, operated by electricity derived from the service lines.

It will be apparent that, by the arrangement described, the thermostat and generator can be plugged into any convenient electric service receptacle, thereby eliminating additional wiring, and that waste of unburnt fuel and the attcndant danger of explosion is also eliminated.

Other objects and advantages of the invention will be found in the description, the drawing, and in the claims; and for full understanding of the invention reference may be had to the following detailed description and accompanying drawing, wherein:

Figure 1 is a. mainly-diagrammatic view of a burner control system embodying my invention;

Figure 2 is a wiring diagram of the carrierfrequency responsive control circuit; and

Figure 3 is a diagram of a modified form of the invention.

Referring first to Fig. 1 of the drawing, the numeral ll indicates a pair of lines II which are assumed to be connected to the usual electrical service, and at the left-hand end of which is an outlet receptacle l2. Plugged into the rece tacle is a control device l3 which comprises a high frequency generator (conveniently operated by energy derived from the service lines), a thermostat, and an electrically operated timer for changing the day and night temperature setting of the thermostat; a. clock, operated by the timer motor, also being included, as is indicated by the clock dial I4. The generator, thermostat and timer may be of any of the well-known types and therefore are not shown in detail. Also connected to the service lines, by wires I5, is an electronic control device l6, shown in detail in Fig. 2, the output of which is connected to a relay I! which controls the energization, by a transformer l8 connected tothe lines ll, of a normally-closed solenoid-operated valve Hi. This valve controls passage of fuel through a conduit 20 to a main burner 2|, where it is'ignited by the flame 22 of a normally constantly-burning pilot burner 23 connected to the valve l9 ahead of its closure. The flame 22, preferably of the semi-luminous type, serves also to illuminate a photocell 24 which is connected by wires 25 to the control device Hi. It will be understood that the thermostat of device I3 serves to switch the high frequency current to the service lines in accordance with the heating requirements.

In Fig. 2 of the drawing, wherein the circuit diagram of the electronic control device I6 is illustrated, the numeral 30 indicates an attachment plug for connecting the circuit to the service lines H at any outlet receptacle convenient to the burner. In the example given, it is to be assumed that the electric service provides cycle alternating current at approximately volts, and that the frequency of the carrier current generated by the device i3 is 15 kilccycles. When the thermostat of device i3 is in circuit-closing condition, the 15 kc. carrierfrequency is applied to the top and bottom wires 3| and 32 of the diagram; these wires also being constantly at the voltage of the service lines. Connected across wires 3| and 32 is a tuned circuit, resonant at 15 kc., comprising a condenser 33 having a value of 0.05 mfd., in series with an inductance c1- choke coil 34 having a value of 2.5 mh. Indicated at 35 is a vacuum tube of the dual type, consisting of a screen-grid amplifier section and a rectifier section. The amplifier section of the tube comprises a control grid 36, a screen grid 37, a cathode 38, and an anode 39; the rectifier section comprising a cathode 40 and an anode 4|. For the sake of simplicity, the necessary cathode heaters have not been shown. The control grid 36 is connected to the junction of condenser 33 and choke coil 34 and thus the 15 kc. carrier voltage is impressed across the control grid and the cathode 38. Due to the low impedance of the choke coil 34 at 60 cycles, the effect of the line voltage upon the control grid is negligible. In series with the cathode 38 is a resistor 42, of low value, which serves to provide the proper grid bias for the amplifier section oi. the tube. The rectifier anode 4| is directly connected to the wire 31, and its cathode is indirectly connected to the other wire 82 through a coil 44, anode 39, and cathode 88, this part of the rectifier circuit being completed by the electron flow in the amplifier section. The rectifier section provides half-wave pulsating direct current for the amplifier anode 89, a condenser 43 of about 4 mid. capacity serving to so smooth the pulsations that the eflect is substantially that of uninterrupted direct current. As has been mentioned, in the circuit of anode 39 is the coil 44 which forms the primary of a coupling transformer 45; the secondary 46 of the transformer being connected to a tuned circuit comprising a condenser 4'1 and a choke coil 48, these elements having the same values, respectively, as those of the condenser 83 and choke coil 34. The characteristics of the transformer 45 should be such that the impedance of its input circuit and of its output or load circuit are substantially matched.

The amplified 15 kc. voltage is applied to a grid-glow rectifier tube 49, the cathode 50 or this tube being connected to the tuned load circuit at the junction of condenser 41 and choke coil 48. The anode of the grid-glow tube is connected, through the coil winding 52 of relay H, to a resistor or voltage divider 53, the opposite ends of which are joined to wires 3| and 32; the connection to the voltage divider being made by an adjustable tap 54. The resistance value of this voltage divider is conveniently about 25,000 ohms. The starter anode 55 of the tube is connected, through a current-limiting resistor 56 having a value of about 0.5 megohm, to another k voltage divider, generally indicated at 51, which The voltage divider 51 is composed of a series.

arrangement of a resistor 59, having a value oi! about 5 megohms, another resistor 50, having a value of about 2 megohms, and the photocell 24. shunted across the relay coil winding 52 is the usual smoothing condenser BI; and across the cathode 50 and starter anode 55 is a small condenser 62 (0.0001 mfd.) which serves to stabilize the operation of the grid-glow tube.

It will be observed that, by the arrangement disclosed, the grid-glow tube is influenced both by the 60 cycle voltage and also by that of the 15 kc. carrier. In initial adjustment of the control circuits of this tube, flow of carrier-frequency current is interrupted, and the 60 cycle voltage across anode 5i and cathode 50 (through the relay coil 52 and choke coil 48) is adjusted by varying the position of the upper tap 54. Assuming that the photocell 24 is fully illuminated by the pilot-burner flame 22 and that consequently its effective resistance in the voltage divider 51 is quite low as compared with that of resistor 60, the other tap 58 is so adjusted that the voltage at the starter anode 55 is just below that at which the tube can fire. If the carrierfrequency current is now permitted to flow, the effect of the additional voltage provided by it (and amplified in tube 35) will cause the gridglow tube to pass current and thereby so energize relay I! that its contact-carrying armature 63 is attracted to connect the transformer l8 to the valve 19 and thus open the same to permit passage of fuel to the main burner 2| where it is ignited by the pilot-burner flame. If, upon establishment of the carrier-frequency current, the tube fails to function as described, the taps 54 asmeoo and 58 are readjusted until the proper 60 cycle voltage conditions are obtained.

lrc. carrier) during the major portion 01 the positive 60 cycle alternation. During the following 60 cycle alternation, the anode will be negative with respect to the cathode and therefore no current will flow. However, during the next 60 cycle positive alternation, current flow will be reinitiated as described-a series of pulsations of direct current thus passing through the relay winding, the condenser 8| serving to so smooth the pulsations that the attractive force on the armature is relatively steady. If the carrierirequency current is interrupted by the thermostat of device l3, starting or the grid-glow tube can no longer occur and the relay I1 is deenergized, thereby effecting closure 01" valve 19. If this valve is of the sensitive type, requiring only a small amount of electrical energy for operation, the relay can be eliminated and the valve-energized directly. If thepilot-burner flame should become extinguished, the efiective-resistance of the photocell 24 in the voltage divider 51 becomes infinite and the 60 cycle voltage or the starter anode is therefore so reduced that firing of the tube is prevented, regardless of the existence of the 15 kc. voltage. It is to be noted that the photo-cell is so arranged that it can pass current during the 60 cycle alternation in which the anode 5l of the grid-glow tube is positive with respect to its cathode 50. Obviously, the carrier-frequencies employed in various control systems should be so chosen that they difier from each other to avoid the possibility of one system aifecting the other when they operate over the same, or adjacent, portions of the service lines. Further, the amount of energy produced by the carrier-frequency generator should be so limited that it is inefiective at great distances.

In the modified form of the invention shown in Fig. 3, the numeral '10 indicates a carrier-irequency responsive control device which may be the same as that shown in the diagram of Fig. 2, except for the elimination of the photocell 24; the resistors 60 and 59 of voltage divider 51 thus being directly in series. The output of the control device is connected, in series with the contact arm H of an additional relay '12, to a relay H which serves to control the energization of the fuel valve in the same manner as relay H in the previously-described form of the invention. The coil winding 13 of relay 12 is connected to a thermoelectric generating device or thermocouple I4, the hot junction I5 of which is arranged to be heated by the pilot-burner flame 22. As long as this flame exists, the generated thermoelectric energy flowing in the ,coil 13 so energizes relay 12 that its contact-arm II is held in the closed position shown, thereby permitting operation of the burner control system in accordance with the demand of the thermostat of device l3. If the pilot-burner flame is extinguished, the control system is rendered inoperative by deenergization of relay 12; the thermoelectric generating device thus serving in the same general manner as the photocell in the other form of the invention. If desired, the switchingmeans of relay 12 could be connected in the voltage divider circuit 51 of Fig. 2 in place of the photocell, to serve a similar P p While I have herein shown and described speciflc embodiments of my invention, I wish it to be understood that modifications may be made without departing from the spirit. of the invention, and that I intend therefore to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a system for controlling the operation of a fluid fuel burner by the aid of carrier-frequency current conducted between the control point and a point adjacent the burner by the electrical service lines: an electrically operated valve located adjacent the burner for controlling fuel supply thereto, means at said control point for generating said carrier-frequency current and including switching means for controlling the connection thereof to said service lines, electrical means connected to the service lines adjacent the valve for supplying electrical energy to the valve, said electrical means including an electronic circuit selectively responsive to said carrier-frequency, and means responsive to the existence of flame adjacent said burner for so controlling said circuit that the electrical means are rendered ineffective 1 to supplyenergy to the valve when the flame is extinguished.

2. A control system, as defined in claim 1 wherein said flame responsive means is a photoelectric cell.

3. In a system for remotely controlling the operation of a fluid fuel burner by the aid of carrier-frequency current conducted between the co trol point and a point adjacent the burner by electrical service lines: a normally-closed electrically operated valve located adjacent the burner for controlling fuel supply thereto; means at said control point and operated by electricity derived from said service lines for generating said carrier-frequency current, said last-named means including temperature responsive switching means for controlling the passage to said service lines of said carrier-frequency current;

electrical means connected to the service lines adjacent the valve for supplying electrical energy to the valve, said electrical means including an electronic circuit selectively responsive to said carrier-frequency; and means responsiv to the existence of flame adjacent said burner for so controlling said circuit that the electrical means are rendered ineffective to supply energy to the valve when the flameis extinguished.

LAcontrol system,asdeflnedinclaim3,

wherein said flan'ie responsive means is a photoelectric cell.

5. In a system for remotely controlling the operation of a fluid fuel burner hy the aid of carrier-frequency current conducted between the control point anda point adjacent the burner by the electrical service lines: a normally-closed electrically operated valve located adjacent the burner for controlling fuel supply thereto; means at said control point and operated by electricity derived from said service lines for generating said carrierfrequency current, said last-named means including temperature responsive switch ing means for controlling passage to said service lines of said carrier-frequency current; electrical means connected to the service lines adjacent the valve for supplying electrical energy to the valve, said electrical means including an electronic circuit selectively responsive to said carrier-frequency; a pilot-burner for said burner; and photoelectric means responsive to the flame of said pilot-burner for so controlling said electronic circuit that only while said flam exists is said electrical means capable of supplying energy to the valve to open the same in response to the demand of said temperature responsive switching means.

6. In a system for remotely controlling the operation of a gas-consuming main burner by the aid of carrier-frequency current conducted between the control point and a point adjacent the burner by the electrical service lines: a normally-closed electrically operated valve located adjacent the burner for controlling fuel supply thereto; means at said control point and operated by electricity derived from said service lines for generating said carrier-frequency current; said last-named means including temperatureresponsive switching means for controlling passage to said service lines of said carrier-frequency current, and also including time-responsive means operated by electricity derived from the service lines for modifying the elect of said temperature-responsive switching means during predetermined periods; electrical means connected to the service lines adjacent the valve for supplying electrical energy to the valve, said electrical means including an electronic circuit selectively responsive to said carrier-frequency; a pilot burner for said main burner; and photoelectric means responsive to the flame of said pilotburner for so controlling said electronic circuit that only while said flame exists is said electrical means capable of supplying energy to the valve wnnm A. RAY. 

